Method of producing gravure etchings



Oct. 26, 1937. A. DULTGEN METHOD OF PRODUCING GRAVURE ETCHINGS vFiled. Aug. 26, 1936 ATTORNEY Patented Oct. 26, 1937 UNITED STATES PATENT OFFICE Arthur Dultgen, Queens Village, N. Y.

Application August 26. 193s, serial Nc. 97,909

Sclaims.

The present invention relates to methods of producing gravure etchings and embodies, more speciiically, an improved method or process wherein gravure etchingsv of a nature far superior to etchings now produced are formed either from half-tone plates or the original subject matter to be reproduced.

'I'he present applicationis in part a continuation of my co-pending application, Serial No. 691,697, iiled September 30, 1933.

In the printing art it is well-known that halftone plates of subject matter to be reproduced.

are produced in great numbers and circulated throughout the country to printing establishments in various locations. The original document or subject matter sov reproduced is maintained generally in one location only and is frequently destroyed after the half-tone plates are produced. If, subsequently, it is desired to reproduce the subject matter by the gravure process, not only is it diillcult to transmit the subject matter to the numerous printing presses located about the country but, as noted above, the original subject matteris frequently unavailable. Inorder that a superior gravure etching may be formed from existing half-tone plates, as well as from other subject matter, the present invention has been designed and an object thereof is to provide an improved process by means of which a gravure etching may be formed from a half-tone plate or other subject matter.

'I'he present invention is of especial value in preparing gravure etchings for color printing. Owing to the inadequacy of color-separation screens, it has been found necessary, in threecolor and four-color processes, to retouch the printing plates by hand after they have been 40 etched photographically. The technique of such hand retouching has been fully developed in connection with half-tone printing plates. With gravure plates on the other hand, such retouching has proved dimcult or impossible. My method may be used to produce gravure plates from half-tone plates which have been retouched by hand. It thus makes possible in gravure printing the use of the results of the technique of half-tone retouching, thereby effecting an important improvement in the quality obtainable in gravure color printing.

An object of the invention is to provide a. method of producing gravure etchings from halftone plates, such etchings being formed with 5 recesses of varying sizes and varying depths in accordance with the flowing tones of the original subject matter. A

Further objects of the invention will be readily apparent as it is described in connection with the accompanying drawing wherein,

Fig. 1 is a flow diagram illustrating the steps of a preferred method embodying the invention; and

Figs. 2, 3, 4 and 5 are similar diagrams showing modified methods embodying the invention. 10

The present half-tone method of producing a printing plate is to place the subject matter to be reproduced before a copying camera and expose the same upon a contrast negative through a screen which is placed in a predetermined po- 15 sition in front of the sensitive plate. The resultant negative will carry the image photographed in the 'shape of half-tone dots of varying size and all of equal transparency. This negative consists either of black opaque dots in 20 a transparent area or transparent dots in a black opaque area. 'I'he negatives are printed upon a sensitized metal plate and etched. In etching all dots will etch at one time (because they are all of equal density or transparency).

The depth of the etching is not important as long as it is sufficiently deep to provide a plate with a printable depth. Incidentally, the etching is done with one strength of acid.

The gravure method of .producing a. printing 30 plate is by exposing, through a copying camera,

a continuous tone or record negative upon a soft working plate (as distinguished from a contrast plate). From this negative a positive is made either through a camera or by contact in 35 a printing frame. No screen is used in forming either the positive or the negative. The positive is printed upon sensitized carbon tissue and after removal, the carbon tissue is placed,v in contact with a gravure screen and exposeda .The 40 tissue is then squeegeed upon a. piece of metal` immersed in warm water, the paper backing stripped off, and the unexposed carbon tissue `then developed or washed of! in warm water. 'This leaves the exposed part of the carbon tissue ad- 45.

hering to the metal which, when dried, is ready for etching. The etching takes place in stages with various strengths of acids, the thinnest deposit of carbon tissue representing the darkest parts of the picture and etching mst in the 5 heaviest acid. As the lighter acids are applied the various tones are etched until the highest lights `(represented by the thickest deposit of carbon tissue) are reached. At this time etching is complete and the etching will be represented by squares of equal area but in depths which vary in accordance with the varying tones from shadows to high lights as in the original.

In` accordance with the present invention, it is proposed in one aspect thereof, to utilize the half-tone method to'produce an acceptable gravure etching and th manner in which the character of the half-tone'etching is changed is such as to change the half-tone dot of fixed-density to a dot of varying density in conformity to the tones of the original subject matter. This may be done by printing the half-tone plate upon a smooth surface paper, preferably with black ink. From the print, a contrast negative is formed, this negative reproducing each dot as it is printed upon the paper. A soft negative is then made upon a continuous-tone plate from the print of the half-tone plate. The dots upon this negative are diffused in such fashion that they reproduce as tones. The soft or continuous-tone plate produces this diffusion of the dot automatically and it may be increased, if desired, by throwing the camera slightly out of focus. 'I'he two negatives -so produced are superimposed and in register A print of this positive upon a piece of carbon I tissue upon which a grain screen has been printed is then made and squeegeed upon a piece of metal which is developed and dried. The etching will be comparable to a gravure etching inasmuch as the shadows will etch first and then the etching will proceed through the varying tones up to the high lights which will etch last. The resultant etching will have a half-tone formation of varying sized dots and a gravure range of varying tones.

As noted above, it is desirable that a grain screen be provided upon the carbon tissue in order that the solid areas which would reproduce in the half-tone plates may be reproduced upon the gravure etching with suitable screen grain formation in order that such areas may hold the ink received therein during the printing operation and prevent the doctor blade from wiping such recesses free of the ink.

The steps of my preferred method whichhas been described (with the exception of the introduction of the grain screen which is not always necessary) are indicated in the ilow diagram, Fig. 1.

My method may be employed to produce gravure printing plates from an original or any other subject matter to combine the half-tone method with the gravure method. Such process tone negative from the subject matter.

:might be carried out by producing a contrast or v.half-tone screened negative and a continuous- These lnegatives are superimposed in register and a positive-is made. 'I'his positive will be composed of each negative (the contrast and the continuOuS- tone negative) and maybe printed separately upon carbon tissue. When the resulting carbon tissue is placed upon metal and etched, the etching will be composed of varying sized dots which vary in depth, as noted above. No grain screen formation is necessary with this method when printing upon carbon tissue, for the reason noted above, and either positive may be printed first.

The invention may also be employed to produce a gravure etching from a half-tone plate, or any other plate formed by a process utilizing a screen, by printing each plate separately upon any transparent or translucent surface. Using a soft working photographic plate or film, a negative of this plate is made through a copying camera. In making this negative the exposure through the camera should be such that the screen dot will be diffused and the resultant negative will have the appearance of a continuous tone. From this negative a positive is made. The positive will register with the original print. 'I'he original print is first printed upon carbon tissue (screened with a grain screen) after which the positive print is printed upon the carbon tissue. The particular order of printing the original or positive may be varied of course. The steps of this modified method are indicated in the ow diagram, Fig. 2.

A modification of this method, which I prefer on account of the very accurate results produced, consists in making the mechanical print from the half-tone plate on the transparent material as an intaglio print. This is done by filling the spaces between the raised dots of the half-tone plate with ink and wiping the ink from the top of the dots before printing, as in intaglio printing. The mechanical print thus made is a negative. From this mechanical print on transparent material, a photographic positive is made by contact printing. Such positive reproduces the halftone dots very clearly and accurately. Using a soft working photographic plate or film, a nega.- tive of this half-tone positive is made through a copying camera in such a way that the dots are diffused, and the resulting negative has the appearance of acontinuous tone. From this negative, a positivev is made. This positive and` the half-tone positive are then printed in register on a carbon tissue (screened with a grain screen), and this carbon tissue is used in the ordinary manner to prepare a gravure plate. Thesteps oi' this modified method are indicated in the flow diagram, Fig. 3.

All of the foregoing methods may be utilized in color printing in which case separate contrast and continuous-tone negatives are made for each color. 'I'here will result two negatives for each color, one being the half-tone screened contrast negative and the other the continuous-tone negative. The two negatives for each color are then superimposed upon each other in register and a positive made. After doing this for each color there will result positives having dots of varying sizes and of varying densities.

The particular type of screen formation, used is, of course, immaterial, as long as it does not conflict with the half-tone screen formation.

Obviously, the particular steps of combining the contrast and continuous tones upon positives or sensitized carbon tissue may be varied without departing from the scope of the present invention deiined in the appended claims. Thus, as indicated above, the contrast image and the continuous-tone image may be combined in a positive which is thereafter printed on a carbon tissue or separate positives may be made from the /two negatives and these may be separately printed on the same carbon tissue. A resist of the combined registered images may also be made Aby making the combination at a later stage in the process. Thus, as indicated in the ilow diagram, Fig. 4, a positive from the contrast negative may be printed upon an ordinary half-tone resist flowed over the plate, and, after finishing the resist in the ordinary manner, a print on carbon tissue from a positivefrom the continuous-tone negative may be reversed and its exposed side applied over this resist in 'register therewith so as to produce a composite resist of the two combined registered images. Alternatively, a positive from each negative may be printed on a separate carbon tissue and these two carbon tissues may be applied in register'to the plate as indicated in the ilow diagram, Fig. 5. In this case, the first carbon tissue is, of course, washed before the second carbon tissue is applied.

It will be noted that, in all the methods which have been described, there is formed on the plate a resist of the two combined registered images which may or may not be a composite resist. The resist, whether or not composite, has permeable areas corresponding in size to the dots of the contrast or sharp image of a half-tone plate and varying in thickness inversely to their size in accordance with the tones of the continuous-tone image.

In the claims which follow, I have for the sake of brevity used the expression blurred image in contradistinction to sharp image to indicate an image which is sufficiently indeiinite or out of focus to lose the half-tone dot formation.

What I claim is:

1. In the process of producing a gravure printing surface from a half-tone printing plate the steps of making a mechanical print from said half-tone printing plate, photographing said print upon a contrast emulsion to produce a sharp image thereof, again photographing said print upon a soft working emulsion suiiiciently out of focus to lose the screen formation and produce a continuous image, superimposing the two images thus produced i'n register, and producing a positive from which the gravure plate may be made in the conventional manner.

2. In the process of producing a gravure printing surface from a half-tone printing plate the steps of making a mechanical print from said half-tone printing plate, photographing. said print upon a contrast emulsion to produce a 5 sharp image thereof, again photographing said print upon a soft working emulsion suiciently out of focus to lose the screen formation but in register with the sharp image so made and produce a continuous image, superimposing the two images thus produced in register, and producing a positive and forming a gravure plate from the positive in theconventional manner with a screen formation thereon.

3, In the process of producing a gravure print- 5 ing plate from a half-tone printing plate, the

steps of making a mechanical print from said half-tone plate, making a sharp transparent image of said print, making a blurred photographic image of said print, and lutilizlng the sharp image to control the areas etched and the blurred image to control the depth of etching in the gravure plate by forming upon a plate a resist of the combined registered images and etching therethrough.

4. In the process of producing a gravure printing plate from a half-tone printing plate, the steps of exposing a carbon tissue to sharp and blurred transparent images of a print from the half-tone plate, applying the exposed side of the carbon tissue toa metal plate, washing the other side of the tissue to produce a resist having separate permeable areas corresponding in size to the dots of the half-tone plate and varying in thickness inversely to their size, and producing the gravure plate by multiple stage etching through this resist.

5. In a process for producing a gravure printing plate having indentations which`fvary both in area and depth in accordance with the tones of subject, the steps of exposing a carbon tissue to a half-tone transparent image and a continuous-tone transparent image of the same subject, applying the exposed side of the carbon tissue to a metal plate, washing the other side of the tissue to produce a resist having separate permeable areas corresponding in size to the dots of the half-tone image and varying in thickness inversely to their size, and producing the gravure plate through multiple stage etching through this resist.

6. In the process ofl producing a gravure printing surface from a half-tone printing plate, the steps of making av mechanical print from said half-tone plate, photographingsaid print upon a contrast emulsion to produce a sharp image thereof, again photographing said print upon a soft working emulsion suiiiciently out of focus to lose the screen formation and to produce a continuous image, reproducing the sharp image on a resist, reproducing the continuous image on car-- bon tissue to provide a resist of variable thickness, `superimposing said resists in register upon a plate and etching the plate through the composite resist thus formed.

7. In a process for producing a gravure printf ing plate having indentations which vary both in area and in depth in accordance with the tones of the subject, the steps of exposing a carbon tissue to a continuous-tone transparent image of the subject, exposing a resist to a halftone transparent image of the subject, applying the exposed side of the carbon tissue to a plate in register with said resist, washing the other side of the tissue to produce a composite resist having separate permeable areas corresponding in size to the dots of the half-tone image and varying in thickness in accordance with the tones of the continuous-tone image, and producing a gravure plate by multiple-stage etching through this resist.

' 8. In the process of producing a gravure printing plate from a half-tone printing plate, the steps of making an intaglio mechanical print from the half-tone plate on transparent material, making a sharp transparent image of said print by contact printing, making a blurred photographic image of said print, and utilizing the shapirnage to control the areas etched and the blurred image to control the depth of etching in thegravure`plate by forming upon a. plate a resist of the combined registered images and etching therethrough.

ARTHUR DULTGEN. 

